A night of drinking turned deadly for a bond trader who got locked out of his West Village penthouse and fell to the street trying to climb onto his balcony from the roof, sources said yesterday.

Though police had not officially ruled out suicide, a police source and neighbors said Matthew Morahan, 29, had told the super he lost his keys — only minutes before he fell at 11:45 p.m. Wednesday.

The Jeffries & Co. trader is thought to have slipped while trying to climb over a three-foot wall that separates a rooftop walkway from his terrace, and plummeted over the side of the building.

He fell 11 floors, crash-landing onto the top of a truck with a bang so loud that 911 callers reported hearing an explosion, cops said.

“It reverberated throughout the entire neighborhood,” said Hannah Hayden, 29.

“I didn’t hear any screaming or arguments, but I heard the sound. It was almost like a car backfiring, but muffled.”

Cops said there was no sign of any struggle. A source said Morahan’s apartment had been searched, but no suicide note was found.

“This guy was very friendly, very happy,” said Ivan Rehder, 41, who lives next door to Morahan’s apartment at 666 Greenwich St. He said his neighbor would go out for drinks every Wednesday night.

“He had a lot of friends. He used to have people over for parties on his terrace.

“This was a tragic accident.”

Morahan had left Merrill Lynch for his job at Jeffries & Co. in December, said Rehder.

He had told friends that he’d managed to avoid the turmoil surrounding the banking world in recent months — and even received a raise recently.

One of his Jeffries co-workers said Morahan’s father had also worked at the company, but had recently retired and was living in Florida. Attempts to contact him and other family members yesterday were not successful.

The co-worker declined to comment further.

Cops and neighbors said the path of Morahan’s fall suggested that he had slipped from the wall. He was believed to be under the influence of alcohol, sources said.

His body was found atop a delivery truck for Creative Party Services, a catering company.

First responders climbed onto the truck to treat him, but he was already dead.